The league’s best blocking receivers?

(10-13) 21:33 PDT — During wide receiver Ted Ginn Jr.‘s 24-yard run on a reverse in Sunday’s win over Tampa Bay, wideout Michael Crabtree served as a convoy, effectively blocking two Buccaneers.

It’s the type of effort that isn’t reflected in the box score, but it didn’t go unnoticed by offensive coordinator Greg Roman. The 49ers have averaged 188.5 rushing yards per game and 6.2 yards per carry over their past two games, and Roman indicated the wideouts deserve some of the credit.

“I challenge anybody to find any NFL receiving corps that blocks as hard and as well as our receivers,” Roman said. “They have been phenomenal. … They are inspiring with their effort.”

Joshua Morgan, who was placed on the season-ending injured reserve list this week, is known as the team’s best blocking wide receiver. But Roman said Crabtree has also been stellar.

Crabtree has been labeled a “diva” wide receiver throughout his career. Roman was asked if divas block downfield like Crabtree.

“What is a diva anyway? I don’t know what that is,” Roman said. “All I can tell you is this: Our receivers are extremely physical in their blocking, and it’s inspiring to everybody.”

Swain familiar with system: Wide receiver Brett Swain said he hopes to play on special teams against the Lions on Sunday, five days after he worked out for the 49ers and subsequently signed a one-year contract.

Swain, who will also serve as the No. 4 wideout, said he’s picking up the offense quickly after spending three years in Green Bay’s West Coast system.

“It’s just a matter of putting the terminology together and learning this team’s rules and their checks and techniques,” he said.

Swain, who worked out for the Bengals earlier this season, acknowledged his tryout with the 49ers was a bit different. For example, coach Jim Harbaugh was among those throwing passes to the receivers who tried out.

“He’s still got a little zip on the ball,” Swain said. “He can spin it a little bit.”

Iupati returns: Left guard Mike Iupati (knee) was limited at practice after sitting out Wednesday. Roman indicated backup Chilo Rachal will play left guard and Adam Snyder will remain at right guard if Iupati can’t play.